Reorganize code from src/ngmx/
Move code for programs that are built from src/ngmx/ into separate subdirectories under src/programs/ and update CMake files accordingly. It remains to be decided where code used in multiple programs should go. There is also some dead code in the directory (e.g., g_highway.c) that should be cleaned up.
Remove g_highway and vbox.c.
g_highway hasn't been included in the build for a long time (never for
CMake), so I don't think anyone will miss it. No need to keep it up to
date with changes done in program initialization for the wrapper binary.
vbox.c seems unused.
There are some other source files under src/ngmx/ that contain a main()
and are not included in the current build, but those seem some kind of
test programs, and don't seem to use much outside src/ngmx/, so left
them alone for now.
Related to #673.
Moved ngmx to C++, renamed it to view.
Part of #673
Moved all files to src/programs/view and made executable
part of the gmx binary as "gmx view".
Replacing min and max by std::min and std::max.
Removed warning in asize macro.
Changed typedef enums to C++ enums.
Changed gmx_bool to bool.
Removed g_showcol, g_xrama, xstat, test_ngmx_dialog